This invention is related to the cleaning of ship tanks and bilges, and more particularly to a closed circuit system and process for cleaning and preparing enclosed large surfaces for recoating.
Closed circuit cleaning of boiler tubes is not unique. However, chemical cleaning of in-place structures is limited due to the difficulty of delivering and controlling hot acid and caustic liquids safely. Shipyards that currently chemically clean ship spaces are strictly required to employ manual hand spray applications with subsequent pump removal of the cleaning liquid. The results are limited and less than desirable due to the constraints on personnel spraying caustic hot liquid and consequently being subjected to vapors, and flooding of the work area. The operations are also limited by safety factors necessitating lower pressure ranges.
Prior methods used a single tank operation which was subject to considerable down-time during mixing and heating stages, and was also susceptible to fluid contamination, requiring subsequent dumping, if foreign matter was returned to the supply tank. The old method of hand spraying limited the allowable volume flow of working fluids and did not allow for sufficiently high pressure applications. In addition, the previous methods which used hydrochloric acid solutions required a crew to enter the tanks to be cleaned and work with hand sprays. The considerable vapors and mists created by spraying are harmful to personnel working in the tanks and performing the cleaning operations.
The system of the present invention for chemically cleaning tanks and bilges provides an automatic process for delivering high pressure and high temperature stripping and cleaning solutions to large surface areas, with consequent recycling of the chemical solutions for repeated pass operations. The invention overcomes the disadvantages inherent in the prior methods and eliminates many of the disadvantages and constraints previously limiting the cleaning operations.